1. Field of the Invention
The present invention relates to hearing devices. More particularly, the present invention relates to in-the-canal hearing devices, wherein a metallic frame expands responsive to body temperature when inserted into the ear canal to ensure a good fit.
The present invention relates to hearing aids and more particularly to an improved hearing aid that utilizes an expandable plug that fits the ear canal of a wearer, the plug carrying a nitinol stent that expands in response to a temperature increase caused by human body temperature, a provided cable (e.g. tube or enabling wire) a connection to be formed between the plug and a hearing aid device (mounted on the outer ear or on a wearer's belt, for example).
2. General Background of the Invention
The hearing industry has desired a one size fits most ear piece to efficiently serve the hearing impaired for many years. Industrial audiologists have also advocated a one-size-fits-most to serve in the hearing protection and communication needs in industry, sport shooting, and military applications. This device has eluded engineers and researchers because the human ear canal is dynamic in nature and is anatomically variant between subjects (indeed, variant from ear to ear).
Each ear canal shape is unique in size, in the directional bend into the head, in geometrical shape (i.e., circular vs. elliptical cross section), and in sensitivity to contact pressure (in the form of a plugged up feeling, in sensations pain, or in reactions of coughing or sneezing). These anatomical variations are a fit problem in combination with dynamic action of the ear canal caused by the rolling, medial to lateral motion of the temperomandibular joint (TMJ) during the opening closing one's mouth. Research has demonstrated that dynamic action of the anterior-posterior plane of the ear canal will vary by about three to five millimeters during talking, chewing, or laughing. These factors, along with the fact that the ear canal slopes upward along the medial plane, deleteriously affect efforts to maintain an acoustic seal in the external ear canal in normal, daily operation of a hearing device.
The challenge to one-size-fits-most is heightened by the secretions of cerumen, oils, and moisture impeding electronic performance and life cycle. The chemical make up of cerumen alone is as individual as the ear in which the end product will reside. Cerumen may vary in acidity, as well as in the content of lipids, proteins, cholesterols, and waxy esters. The content latter component will, in fact, determine whether a wearer's cerumen is “wet” or “dry” in nature, each of which presents a different problem for hearing instrument longevity.
From a psycho-acoustic perspective the location and pressure of the acoustic seal is very important. Poor placement will cause a sense of occlusion or stuffiness in the ear. The occlusion effect is the result of soft-tissue-conducted sounds that create an internal sound level greater than 10-12 dB above the ambient (or “out-side” of the head) sound levels. When this occurs, wearers report their own voices sounding funny, hollow, or as if their heads are in barrels. This is commonly caused by too tight an acoustic seal on soft tissue between the aperture medially to the first directional bend of the external ear canal. Occlusion effect is further heightened by varied peripheral or “slit leakage” and poor or no venting. The slit leakage facilitates annoying low frequency resonation and distorts the mid-frequency sounds. Conversely, these problems are best managed with good venting and uniform acoustic seal.
When the acoustic seal is created properly at a point in the ear canal where there is a balance of cartilaginous and bony material, there is less slit leakage, sound is natural, and acoustic feedback is avoided. By adding a well designed vent system to allow excess low frequency sound energy to roll-off, and undesireably high ear canal air pressure to be released, the hearing device is optimized in all applications. The over-all performance of the device can then yield better sound quality and “distinctness of sounds.”
With the goal of high fidelity amplification in both custom and non-custom hearing instruments, entailing a 20-20,000 Hz frequency response, a dynamic, secure, yet comfortable acoustic seal is paramount.
All previous efforts to achieve this type of fit have revolved around the concept of building up the exterior of the hearing instrument, making a “tighter” fit. This approach, unfortunately, was the only avenue available with those instruments composed of rigid, non-compliant acrylic.
The traditional shell molded from an individual's unique ear impression has not yielded a truly typical form that anatomically fits a significant percentage of any external ear category. It is further limited by a dated acrylic design which is the most commonly used shell technology. This technology was adopted from dental industry in the 1960's. It has a Shore Hardness factor of 90 Durometer. Little design change has been introduced since its development. Production and curing techniques have improved, however, through laser modeling and 3-D imaging. Since the ear is a dynamic acoustic environment and is ill-served by a rigid material like acrylic. The material however has a reasonable life cycle in the environment of the ear. Hard Durometer devices rock in the ear with jaw motion (TMJ), as opposed to flexing and accommodating the dynamic action of the ear.
Attempts with soft hollow shell technology have failed based on several key issues: Most soft material shrinks, discolors (usually unsightly yellow or brown), hardens after a few months.
Silicone based materials, which are preferred to be used in the body, are incompatible for bonding to the typical electronic faceplate. Soft/hollow materials tend to collapse upon insertion and deform over time loosing their ability to create an acoustic seal.
Foam technology typically requires multiple sizes to achieve a fit. They are uncomfortable, stuffy, and should not be reused as cellular foam becomes a breeding ground for bacteria.
Hearing aids are supplied in many types and configurations. One example of a hearing aid is the common behind-the-ear or “BTE” style hearing aid that hooks upon the outside surface of a user's ear. Another type of hearing aid is an in-the-ear type hearing aid that is entirely contained within the ear canal of a wearer. With the in-the-ear style hearing aid, an external plate is mounted at the outer surface of the ear and providing controls for enabling the wearer to change the volume of the hearing aid.
Some people do not like the in-the-ear style hearing aid. Some users have the degree of hearing loss where beneficial gain before feedback cannot be achieved with traditional in-the-ear hearing aids. Other users dislike the appearance of those custom fit in-the-ear hearing aids, and find them very unattractive. Still others find that in-the-ear hearing aids are prone to cerumen-related failures requiring frequent repairs. Others prefer the larger electronics package that can be placed in a behind-the-ear type hearing aid. BTE hearing aids generally provide much more power before feedback. They also, because of increased size, offer more features (e.g. frequency shaping potentiometers). They can also prove to be easier to adjust for those users with impaired dexterity. In addition, and also because of their size, BTE hearing aids are amenable to interfacing with assistive listening devices, and with communication devices. Finally, BTE devices rarely fail because of cerumen; the cerumen is accreted in the ear mold, which is usually easy to clean.
The following US patents are each hereby incorporated herein by reference:
U.S. Pat. No. 6,478,656 Method and apparatus for expanding soft tissue with shape memory alloys; This patent describes the application of a body worn bra where by the soft tissue of the skin forming the breast is expanded by incorporating an adhesive and an appliance with a shape memory alloy.
U.S. Pat. No. 6,135,235 discloses a self-cleaning cerumen guard for a hearing device.
U.S. Pat. No. 5,999,859 discloses a apparatus and method for perimodiolar cochlear implant with retro-positioning.
U.S. Pat. No. 5,977,689 discloses a biocompatible, implantable hearing aid microactuator.
U.S. Pat. No. 5,800,500 discloses a cochlear implant with shape memory material and method for implanting the same.
U.S. Pat. No. 5,772,575 discloses an implantable hearing aid.
U.S. Pat. No. 5,630,839 discloses a multi-electrode cochlear implant and method of manufacturing the same.
U.S. Pat. No. 4,762,135 discloses a cochlea implant.
U.S. Pat. No. 3,865,998 discloses an ear seal. This patent states that the typical cross section of the external ear canal is best approximated by a super ellipse which is defined by the equation: (x/a)n+(y/b)n=1 where n=2.4. The hypothesis is that an ear seal could be created using a soft material with an outer periphery defined by the super elliptic shape. The patent does not address the bigger issues associated with the longitudinal axes formed by extending a line through the medial-lateral plane or the dynamic nature of the TMJ. The latter issue was neglected because the device was very short by today's standards for insertion. The patent also did not consider the surface pressure necessary to create the acoustic seal it desired to deliver. In essence it was a tapered flanged silicone plug of super ellipse cross section.
Incorporated herein by reference are all patent applications and patents naming one or more of us as inventors.
Nitinol wire is used in a variety of medical and nonmedical device applications including guide wires, catheters, stents, filters, orthodontic appliances, eyeglass frames, cellular phone antennae and fishing tackle, to name a few.
Because shape memory and super elasticity are very temperature dependent, the fully annealed austenitic peak temperature is used to classify Nitinol to set the transformation temperature at which the Nitinol material has completely transformed to its memory shape or below which, exhibits malleable, ductile characteristics.
Of the many mechanical properties unique to Nitinol, two critical characteristics exhibited in the austenitic phase are the loading plateau and the unloading plateau, usually diagrammed on a stress/strain curve. The loading plateau is the stress level at which material produces an almost constant stress level over a relatively large range of strain, up to about 8%. Stainless steel conversely, does not exhibit this property of constant stress after 0.3% of strain. Other information relating to Nitinol can be found at www.nitinol.com.